Sash clamps are used to clamp work together when it
is glued. They vary in size and are normally used in pairs. The lengths
are normally from 460mm to 1370mm. The bar is made from cold drawn mild
steel and the head and slides made from malleable iron.

When in use, the sash clamp is placed below the work
to be glued / assembled. The slides are arranged on either side and
scrap wood is placed between each face and the work. This protects the
work when the thread is tightened. The tommy bar is used to tighten the
thread and pressure is increased slowly.

After clamping a frame, the 'squareness' of the frame
should be tested and adjustments made to the position of the clamps if
necessary. The internal angles of the corners should be 90 degrees. The
90 degree angle is checked with a try square or a rule. A long ruler is
used to check large frames and a try square is used on smaller ones.
When using a ruler the diagonal distances are measured. If both
measurements are the same, the angles at each corner are correct. If the
two measurements differ, the clamps need adjusting until the
measurements are the same.

A RULER BEING USED TO
CHECK
FOR 90 DEGREE ANGLES

A try square is pushed into the each corner of a
smaller frame / box, to check that the 90 degrees internal angle is
correct.

QUESTIONS:1. Draw a typical sash clamp and
label the important parts.2. Using diagrams and notes, explain
how a pair of sash clamps are used to ‘clamp together’ a frame / box.3. Describe how the internal angles
of a frame are checked, after sash clamps have been tightened in
position.4. What could happen if the internal
angles are not checked and the frame is glued together?